1. Technical Field
The present invention relates to a liquid ejecting head. More specifically, the present invention relates to a liquid ejecting head that ejects liquid through a nozzle opening, a liquid ejecting apparatus, and an actuator device.
2. Related Art
In some of piezoelectric elements currently used in liquid ejecting heads, a piezoelectric material layer made of a piezoelectric material exhibiting an electromechanical transducing function such as, for example, a crystalline dielectric material, is disposed between two electrodes. An example a liquid ejecting head which uses such an actuator is an ink jet recording head which has a pressure generating chamber communicating with a nozzle opening that ejects an ink droplet. A part of the pressure generating chamber is constituted by a diaphragm and the diaphragm is deformed by a piezoelectric element, so as to pressurize ink in the pressure generating chamber and to eject an ink droplet through the nozzle opening. The use of piezoelectric elements in ink jet recording heads is known in the art. In such a piezoelectric element, for example, a piezoelectric material layer is uniformly formed over an entire surface of a diaphragm by using a film forming technology. The piezoelectric material layer is cut to be divided into parts having a shape corresponding to a pressure generating chamber so as to form independent piezoelectric elements for the respective pressure generating chambers using a lithography method. One example of such a configuration is disclosed in JP-A-2003-127366 at pages 4 to 7 and in FIGS. 1 to 4.
One problem with this configuration, however, is that since the piezoelectric material forming the piezoelectric material layer repeatedly undergoes rotational expansion and contraction of polarization during its operation, a so-called wear phenomenon may occur where the orientation of the polarization becomes partially fixed so as to follow an electric field application direction as time passes, resulting in the decrease in the piezoelectric displacement amount. In a case where such a piezoelectric element is used, for example, in a liquid ejecting head, the piezoelectric displacement amount varies in accordance with the use of the liquid ejecting head so that it is difficult to perform stable ejecting of the liquid.
The above problem arises not only in an actuator device used in an ink jet recording head and other liquid ejecting heads but also in an actuator device mounted in other types of devices.